Antenna system for providing coverage from a high-altitude platform

ABSTRACT

Aspects of the disclosure provide an antenna system for a high-altitude platform (HAP). The antenna system may include a central panel including a first set of antenna elements. The antenna system may also include a plurality of auxiliary panels arranged around the central panel and at an angular offset from the central panel. Each auxiliary panel of the set of auxiliary panels may include a second plurality of antenna elements. The first plurality of antenna elements may be configured to provide network coverage within a first area having a first radius and each of the second sets of antenna elements are configured to provide network coverage within a second area beyond the first radius.

BACKGROUND

Information can be transmitted over directional point-to-point networksor point-to-multipoint networks, such as aerospace and other mobilenetworks. In such networks, links can be formed between pairs of nodesby aiming transceivers of each node pair towards each other. In someimplementations, nodes may include non-geostationary satellite orbit(NGSO) satellites or other high-altitude platforms (HAPs) that are inmotion relative to the Earth.

BRIEF SUMMARY

The technology described herein provides for an antenna systemconfigured to provide coverage from a high-altitude platform. Theantenna system may be configured to provide coverage to a plurality ofsectors in a large geographic area from a low earth orbit. One aspect ofthe disclosure provides a system including an antenna system for ahigh-altitude platform (HAP). The antenna system includes a centralpanel including a first set of antenna elements; and a plurality ofauxiliary panels arranged around the central panel and at an angularoffset from the central panel. Each auxiliary panel of the plurality ofauxiliary panels includes a second set of antenna elements. The firstset of antenna elements are configured to provide network coveragewithin a first area having a first radius and each of the second sets ofantenna elements are configured to provide network coverage within asecond area beyond the first radius.

In one example, the plurality of auxiliary panels includes at least 4auxiliary panels. In another example, the plurality of auxiliary panelsincludes at least 12 auxiliary panels. In another example, the centralpanel is arranged such that when in operation on the HAP, the centralpanel is oriented or faces in a downward direction relative to the HAP.In this example, the plurality of auxiliary panels are arranged suchthat when in operation on the HAP, the plurality of auxiliary panels areoriented at an angle offset from the downward direction relative to theHAP corresponding to a downward tilt. In addition, the downward tilt isa fixed orientation. Alternatively, the downward tilt is an adjustableorientation. In another example, the plurality of auxiliary panels arearranged such that when in operation on the HAP, the central panel isrecessed relative to the auxiliary panels. In another example, thecentral panel includes a planar surface on which the first set ofantenna elements are arranged. In another example, the central panel isa ring. In another example, the first set of antenna elements arearranged at regular intervals around the central panel. In anotherexample, each of the plurality of auxiliary panels. In another example,each of the second sets of antenna elements are arranged in a lineararray on a respective one of the plurality of auxiliary panels. Inanother example, each of the second sets of antenna elements has aclover-shape. In another example, each of the plurality of auxiliarypanels has a same configuration. In another example, the system alsoincludes one or more processors configured to electronically steer apointing direction of a beam formed by the first set of antennaelements. In another example, the system also includes a gimbalconfigured to adjust an orientation of the central panel relative to theHAP and thereby steer a pointing direction of a beam formed by the firstset of antenna elements. In another example, the plurality of auxiliarypanels are arranged such that when in operation on the HAP, the centralpanel is arranged below the auxiliary panels. In another example, thesystem also includes the HAP. In this example, the HAP includes aballoon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial diagram of a portion of an example network inaccordance with aspects of the disclosure.

FIG. 2 is a functional diagram of nodes of the network shown in FIG. 1in accordance with aspects of the disclosure.

FIGS. 3A and 3B are an example configuration of an antenna system inaccordance with aspects of the disclosure.

FIG. 4 is an example configuration of an antenna system in accordancewith aspects of the disclosure.

FIG. 5 is an example configuration of an antenna system in accordancewith aspects of the disclosure.

FIG. 6 is an example representation of a coverage area in accordancewith aspects of the disclosure.

FIG. 7 is an example coverage area configuration in accordance withaspects of the disclosure.

FIG. 8 is an example coverage area configuration in accordance withaspects of the disclosure.

FIG. 9 is an example switching system in accordance with aspects of thedisclosure.

DETAILED DESCRIPTION Overview

The technology relates to a communication system on a high-altitudeplatform (HAP) for providing coverage over a large geographic area. Thelarge geographic area may have a first radius on the order of tens ofkilometers. To provide coverage over the large geographic area, thecommunication system may include an antenna system designed to point aplurality of spot beams radially about the HAP at a downward anglerelative to the HAP. The antenna system may also be configured to pointat least one spot beam directly downward relative to the HAP. The spotbeams may be independently or collectively steerable. The steering ofthe spot beams may be performed mechanically and/or electronically.Using this antenna system, the communication system may be able toprovide coverage to the entirety of the large geographic area in anefficient manner.

The antenna system for the communication system of the HAP may include aplurality of antenna elements in a split arrangement. The splitarrangement may comprise a central panel and at least one auxiliarypanel. The central panel includes a set, or an array, of antennaelements and is installed facing downward relative to the HAP. The setof antenna elements may be arranged in a planar array on the centralpanel, and the central panel may be normal to a downward directionrelative to the HAP. Each auxiliary panel includes another set ofantenna elements and is installed about the central panel with adownward tilt relative to the HAP. The downward tilt may be a mechanicaltilt or an electronic tilt.

In this split arrangement, the antenna system may provide coverage in afirst sector directly below the HAP using the set of antenna elements onthe central panel. The first sector may have a second radius smallerthan the first radius of the large geographic area. For a plurality ofauxiliary elements, the set of antenna elements on each auxiliaryelement may be used in the antenna system to provide coverage to asector covering a portion of the area between the first radius and thesecond radius.

In some implementations, the set of antenna elements on the at least oneauxiliary panel may also be steered to narrow or widen the area ofcoverage provided by the at least one auxiliary panel. The width of thearea of coverage may also be determined based on population density,history of demand, presence of other terminals (terrestrial towers,other HAPs, etc.) providing coverage in or near the area, or othernetwork factors. Additionally or alternatively, the central panel may besteerable. In another alternative, a separate steerable antenna may bemounted on the HAP in addition to or in place of the central panel. Theseparate steerable antenna may be configured to provide narrow, highcapacity coverage to a smaller geographic area within the largegeographic area.

The features described herein may provide for a communication systemthat, when mounted on a HAP, increases coverage and capacity for anetwork. The antenna system may reach areas tens of kilometers in radiuswith more consistent, low capacity coverage and may also be used fornarrower, high capacity coverage for particular areas with a need forgreater bandwidth. As described, the communication system may flexiblyadapt to different network needs for a geographic area and may conserveresources as a result.

Example Network

FIG. 1 is a pictorial diagram of an example system 100 of network nodesin a network. The network may include nodes mounted on variousland-based and air-based devices, some of which may change position withrespect to other nodes in the network over time. For example, as shownin FIG. 1, the network includes as nodes a first terrestrial tower 110and a second terrestrial tower 112. The network also includes as a nodea high-altitude platform 114. As shown, HAP 114 is a balloon. In otherembodiments, the HAP may be a blimp, an airplane, an unmanned aerialvehicle (UAV) such as a drone, a satellite, or another platform capableof low Earth orbit. The network nodes as shown in FIG. 1 areillustrative only, and the network may include additional or differentnodes. For example, in some implementations, the network may includeadditional HAPs and/or additional terrestrial towers. When the networkincludes at least one low Earth orbit or high Earth orbit satellite aswell as one other type of HAP, the network may be defined as a hybridHAP/satellite network.

Nodes in the network may be equipped to transmit and receive mmWavesignals or other very high frequency signals. Additionally oralternatively, nodes in the network may be equipped to transmit andreceive other radio-frequency signals, optical signals, or othercommunication signal capable of travelling through free space. In thisregard, the system may include any number of possible paths for atransmitted communication signal to pass through the network.

The dashed-line arrows of FIG. 1 shown projecting from nodes representpossible paths 120, 122 a, 122 b, 124, 126, 128, 130 for a transmittedcommunication signal. As shown in FIG. 1, some possible paths may beblocked by buildings, such as buildings 140, 142. For example, a signalfollowing path 120 from node 110 may be angled below the horizon and beblocked by building 140. A signal following path 122 a from node 110 maybe angled above path 120, avoiding building 140, but then may contactbuilding 142. The signal following path 122 a may reflect off building142 and follow path 122 b towards the ground location of a user 150,carrying a client device 152. A signal following path 124 from node 110may be angled towards or above the horizon, nearly parallel to theground, passing over building 140, but then may be blocked by building142. A signal following path 126 from node 110 may be angled above thehorizon and reach node 114. A signal following path 128 from node 114directed to the ground location of user 150. A signal following path 130from node 114 may be angled below the horizon, pass over building 142,and reach node 112.

In addition, a signal transmitted from the client device 152 of the user150 back towards one or more nodes of the network. For example, a signalfrom the client device 152 may be transmitted back along paths 122 b and122 a towards node 110. Another signal from the client device 152 may betransmitted back along path 128 towards node 114. In addition, multipleusers or multiple client devices may form bi-directional access linkswith a given node of the network at a given point in time, in additionto the user 150 and the client device 152 shown in FIG. 1.

In some implementations, the network may serve as an access network forclient devices such as cellular phones, laptop computers, desktopcomputers, wearable devices, or tablet computers. For example, nodes110, 112, 114 may connect to the datacenters via wireless, fiber, orcable backbone network links or transit networks operated by thirdparties. The nodes 110, 112, 114 may provide wireless access for users,such as user 150, and may forward user requests to the datacenters andreturn responses to the users via the backbone network links.

As an example, the first terrestrial tower 110, the second terrestrialtower 112, and the HAP 114 may include wireless transceivers configuredto operate in a cellular or other mobile network, such as 5G NR (newradio) networks or LTE networks. The nodes 110, 112, 114 may operate asgNodeB stations, eNodeB stations, or other wireless access points, suchas WiMAX or UMTS access points. One or more terrestrial towers in thenetwork may include an optical fiber or other link connecting the one ormore terrestrial towers to another terrestrial tower or datacenter. Forexample, the second terrestrial tower 112 may include fiber 113, shownby a dashed-line arrow, that connects to another terrestrial tower (notshown). In addition, the user 150 may be carrying a client device 152which may be configured to communicate with one or more of the nodes inthe network. The network also may be connected to a larger network, suchas the Internet or other public or private networks, and may beconfigured to provide a client device with access to resources stored onor provided through the larger network.

In some implementations, the network can be a software-defined network(SDN) that is controlled by an SDN network controller. The SND networkcontroller may be located at one of the network nodes or at a separateplatform, such as, for example, in a datacenter. The nodes of thenetwork, including nodes 110, 112, 114 may be configured to communicatewith one another using steerable transceivers. As the HAPs in thenetwork, such as HAP 114, move with respect to other nodes in thenetwork, such as terrestrial towers 110, 112, some network links maybecome infeasible due to range of the transceivers or obstacles betweenthe nodes. Thus, the configuration of the network may require regular(i.e., periodic) or irregular reconfiguration using the networkcontroller to maintain connectivity and to satisfy determined networkflows.

Example Systems

As shown in FIG. 2, each node, such as first terrestrial tower 110,second terrestrial tower 112, and HAP 114, may include one or moretransceivers configured to transmit and receive communication signalsand create one or more communication links with another node in thenetwork. Referring to HAP 114 as an example, each of the nodes, mayinclude one or more processors 210, memory 212, an antenna system 218,and one or more transceivers 220. In this regard, the processors,memory, antenna system, and transceivers of first terrestrial tower 110and second terrestrial tower 112 may be configured the same as orsimilarly to those of the HAP 114. While only terrestrial towers 110,112 and HAP 114 are shown, other terrestrial towers and HAPs in thenetwork may have the same or as similar configurations.

The one or more processors 210 may be any conventional processors, suchas commercially available CPUs. Alternatively, the one or moreprocessors may be a dedicated device such as an application specificintegrated circuit (ASIC) or other hardware-based processor, such as afield programmable gate array (FPGA). The one or more processors 210 maybe configured to operate according to a given protocol architecture fora mobile network, such as 5G NR architecture or LTE radio protocolarchitecture. Although FIG. 2 functionally illustrates the one or moreprocessors 210 and memory 212 as being within the same block, it will beunderstood that the one or more processors 210 and memory 212 mayactually comprise multiple processors and memories that may or may notbe stored within the same physical housing. Accordingly, references to aprocessor or computer will be understood to include references to acollection of processors or computers or memories that may or may notoperate in parallel.

Memory 212 may store information accessible by the one or moreprocessors 210, including data 214, and instructions 216, that may beexecuted by the one or more processors 210. The memory may be of anytype capable of storing information accessible by the processor,including non-transitory and tangible computer-readable mediumscontaining computer readable instructions such as a hard-drive, memorycard, ROM, RAM, DVD or other optical disks, as well as otherwrite-capable and read-only memories. The system and method may includedifferent combinations of the foregoing, whereby different portions ofthe data 214 and instructions 216 are stored on different types ofmedia. In the memory of each node, such as memory 212 of HAP 110 a, aforwarding information base or forwarding table may be stored thatindicate how signals received at each node should be forwarded, ortransmitted. For example, the forwarding table stored in memory 212 mayindicate that a signal received from ground station 107 a should beforwarded to HAP 110 d.

Data 214 may be retrieved, stored or modified by the one or moreprocessors 210 in accordance with the instructions 216. For instance,although the system and method are not limited by any particular datastructure, the data 214 may be stored in computer registers, in arelational database as a table having a plurality of different fieldsand records, XML documents or flat files. The data 214 may also beformatted in any computer-readable format such as, but not limited to,binary values or Unicode. By further way of example only, image data maybe stored as bitmaps comprised of grids of pixels that are stored inaccordance with formats that are compressed or uncompressed, lossless(e.g., BMP) or lossy (e.g., JPEG), and bitmap or vector-based (e.g.,SVG), as well as computer instructions for drawing graphics. The data214 may comprise any information sufficient to identify the relevantinformation, such as numbers, descriptive text, proprietary codes,references to data stored in other areas of the same memory or differentmemories (including other network locations) or information that is usedby a function to calculate the relevant data.

The instructions 216 may be any set of instructions to be executeddirectly (such as machine code) or indirectly (such as scripts) by theone or more processors 210. For example, the instructions 216 mayinclude the given protocol architecture for the mobile network of whichthe node is a part. The given protocol architecture may include a splitarchitecture between a central unit and a distributed unit. In addition,the given protocol architecture may define a control plane, a userplane, or other protocol layers. The given protocol architecture mayalso include an interface that defines a plurality of messages for usein communication between the protocol layers. The instructions 216 maybe stored as computer code on the computer-readable medium. In thatregard, the terms “instructions” and “programs” may be usedinterchangeably herein. The instructions 216 may be stored in objectcode format for direct processing by the one or more processors 210, orin any other computer language including scripts or collections ofindependent source code modules that are interpreted on demand orcompiled in advance. Functions, methods and routines of the instructions216 are explained in more detail below.

The one or more transceivers 220 may include at least one wirelesstransceiver mounted to actuators that can be controlled, or steered, topoint in a desired direction. To form a wireless link between two nodes,such as the node associated with the HAP 114 and the node associatedwith the first terrestrial tower 110, the wireless transceivers of therespective nodes can be controlled to point in the direction of oneanother so that data can be sent and received between the nodes. Fornodes with fiber or cable connections, such as second terrestrial tower112, the one or more transceivers 220 may also include at least onetransceiver configured to communicate via a fiber or cable connection.

As further shown in FIG. 2, the client device 152 associated with user150 may be a personal computing device or a server with one or moreprocessors 250, memory 252, data 254, and instructions 256 similar tothose described above with respect to the one or more processors 210,memory 212, data 214, and instructions 216. As an example, a personalcomputing devices may include a personal computer that has all of thecomponents normally used in connection with a personal computer such asa central processing unit (CPU), memory (e.g., RAM and internal harddrives) storing data and instructions, an electronic display (e.g., amonitor having a screen, a small LCD touch-screen, a projector, atelevision, or any other electrical device that is operable to displayinformation), user input (e.g., a mouse, keyboard, touch screen ormicrophone), camera, speakers, a network interface device, and all ofthe components used for connecting these elements to one another.Personal computing devices may also include mobile devices such as PDAs,cellular phones, and the like. Indeed, client device 152 may be anydevice capable of processing instructions and transmitting data to andfrom humans and other computers including general purpose computers,network computers lacking local storage capability, and set top boxesfor televisions. In some embodiments, client devices may be associatedwith one or more SDN applications and may have one or more northboundinterface (NBI) drivers.

The antenna system 218 of the HAP 114 may include a plurality of antennaelements in a split arrangement. For instance, the antenna system 218may include a central panel and at least one or a plurality of auxiliarypanels arranged at an angle offset from the central panel. Turning toFIG. 3A, which provides a partial representative view of an exampleconfiguration of the antenna system 218, includes a central panel 310and four auxiliary panels 320, 322, 324, 326 (only 3 are visible in theview of FIG. 3A) at an angle offset from the central panel 310 and adownward direction (toward the ground) relative to the HAP 114. Forinstance, turning to FIG. 3B, which provides a bottom-up view of theantenna system 218, four auxiliary panels 320, 322, 324, 326 arearranged around a central panel 310. Although this example depicts moreauxiliary panels, more, such as 8 or 12 (as shown in FIGS. 4 and 5), orless, such as 2 or 1, auxiliary panels may be used.

The central panel may include a set, or an array, of antenna elements.The central panel may be installed on the HAP 114 such that when inoperation, the central panel is oriented or faces in a downwarddirection relative to the HAP 114. The set of antenna elements may bearranged in a planar array on the central panel, and when in operation,the central panel may be oriented in a plane that is normal to thedownward direction relative to the HAP 114. In this regard, the set ofantenna elements may be configured to point at least one spot beam inthe downward direction relative to the HAP 114. The spot beams may beindependently or collectively steerable as discussed further below. Forexample, in a situation in which an HAP is proximate to a particularcity, beams may be pointed towards the city in order to provide coverageto the city or away from the city in order to prevent interference toterrestrial towers in the city. This decision can be made independentlyon different directions of the HAP, depending on city locations aroundthe HAP.

Each auxiliary panel includes another set of antenna elements and isinstalled about the central panel with a downward tilt relative to theHAP 114. The downward tilt may be structural (e.g. a fixed orientation)or alternatively, an electronic tilt (e.g. an adjustable orientation) asdiscussed further below. In this regard, the set of antenna elements ofthe auxiliary panels may each be configured to point at least one spotbeam at an angle that is offset from the at least one spot beam of theset of antenna elements of the central panel or not directly downwardrelative to the HAP 114.

The sets of antenna elements of each auxiliary panel and/or the centralpanel may have various configurations. For instance each panel may have3, 4, 5 or more sets of antenna elements.

The central panel may have any number of different configurations. Thecentral panel may be mounted below the at least one auxiliary panel asdepicted in FIGS. 3A and 3B or may be recessed relative to the auxiliarypanels. The central panel 310 may include a planar surface holding theset of antenna elements. For instance, the central panel may include arectangular, circular, or another planar shape having a center point. Inanother example configuration of the antenna system 218, depicted inFIG. 4, a central panel 410, which may include various of the featuresof central panel 310 described above, may be a planar ring mounted aboveat least one auxiliary panel. In this example, there are 12 auxiliarypanels 420-431, each including a set of antenna element 440, 442, 444,446, 448 (only those of auxiliary panel 423 being called out forsimplicity). In addition, antenna elements 450, 452, 454, 456, 458 (onlya few being called out for simplicity) of the central panel 410 may bearranged at regular intervals around the planar ring, pointing directlydownward relative to the HAP 114.

The at least one auxiliary panel may comprise a single cylindrical,conical, parabolic a planar, rectangular panel with antenna elementsarranged about the panel, or may comprise a plurality of auxiliarypanels that each hold a separate set of antenna elements. In addition,when a plurality of auxiliary panels are used, such as in the examplesof FIGS. 3A, 3B, and 4, the auxiliary panels may all have theconfiguration, for instance, same dimensions and hold a same arrangementof antenna elements. In some instances, the antenna elements may bearranged on a rectangular auxiliary panel in a linear array along thelength of the auxiliary panel. For example, there may be five antennaelements arranged along each auxiliary panel as shown in the example ofFIG. 4. Alternatively, each auxiliary panel may have 3 or 4 or moreantenna elements.

In some examples, each antenna element on the auxiliary panel may beclover-shaped. In another example configuration of the antenna system218, depicted in FIG. 5, a central panel 510, which may include variousof the features of central panels 310 and/or 410 described above, may bea planar ring, a rectangular array of antenna elements, or a circulararray of antenna elements mounted above at least one auxiliary panel. Inthis example, there may be 12 auxiliary panels 520, 522, 523, 524, 525,though only 5 are visible in the view of FIG. 5. In this example, eachauxiliary panel include four antenna element 540, 542, 544, 546 (onlythose of auxiliary panel 523 being called out for simplicity). Again,antenna elements 550, 552, 554, 556, 558 (only a view being visible inthe view of FIG. 5) of the central panel 510 may be arranged at regularintervals around the planar ring, pointing directly downward relative tothe HAP 114.

As an alternative configuration to the example of FIGS. 3A, 3B, 4 and 5,different numbers of auxiliary panels may be used. For instance, insteadof 4 or 12 auxiliary panels with 5 elements each, 6 auxiliary panels maybe used. As compared to the examples of FIGS. 4 and 5, this would changethe digital beam forming coefficients and would also change the antennagain, but would still be functional for the uses described herein.Again, as noted above, any number of auxiliary panels may be used.

The auxiliary panels may be installed at regular intervals about an axisperpendicular to and centered on the central panel. For example, whenthere are four auxiliary panels (such as in the examples of FIGS. 3A and3B), the first auxiliary panel may point in a first direction, thesecond auxiliary panel may point in a second direction rotated 90degrees about the axis from the first direction, the third auxiliarypanel may point in a third direction rotated 90 degrees about the axisfrom the second direction, and the fourth auxiliary panel may point in afourth direction rotated 90 degrees about the axis from the thirddirection. When there are twelve auxiliary panels (such as in theexamples of FIGS. 4 and 5), each panel may be rotated about the axis by30 degrees relative to a neighboring panel.

The auxiliary panels may be oriented perpendicular to the central paneland may be configured to point downward relative to the HAP usingelectronic steering. For instance, standard digital or analogbeamforming techniques can be used to achieve beam steering. Digitalbeam forming may require an RF path for each element, whereas analogbeam forming can be done by using analog phase shifters. Other analogbeamforming methods will use butler matrices. Yet another analog beamforming approach having different combining circuits may be used.Alternatively, reflector antennas with multiple feeds may be used. Inthis example, different feed architectures may be used such that theantenna elements themselves can be steered. For example, one or moreprocessors may be configured to perform beam forming for the set of 5antenna elements on a given auxiliary panel to form a beam pointing atapproximately 60 degrees toward the horizon. Alternatively, theauxiliary panels may be mounted to be angled away from the central panel(such as in the example of FIGS. 3A and 3B), such that the antennaelements on the auxiliary panels are tilted downward relative to theHAP.

As shown in FIG. 6, in the split arrangement, the antenna system 218(using any of the examples of FIG. 3A, 3B, 4 or 5) may provide coveragein a first sector 610 directly below the HAP 114 using the set ofantenna elements on the central panel. The first sector 610 may have asecond radius smaller than a first radius of a large geographic area620. The set of antenna elements on the central panel 310 may beconfigured to form a beam having a beam width of approximately plus orminus 50 degrees (i.e. 100 degrees in total) about a center of thecentral panel or an axis corresponding to the direction of gravity asdepicted by arrows 312, 314 and angle θ1 in the example of FIG. 3A.Angles of greater than 50 degrees may also be possible; however, thismay lead to large side lobes and large directivity loss. Returning toFIG. 6, the first radius of the large geographic area may beapproximately 80 kilometers. As an example, when the HAP 114 is flyingat approximately 20 kilometers above the large geographic area 620, thesecond radius of the first sector may be approximately 20 kilometers. Inaddition or alternatively, the first sector may be subdivided into aplurality of sectors formed by the central panel as discussed withrespect to FIGS. 7 and 8 below. These sectors may each be within plus orminus 50 degrees of elevation relative to a center of the central panelor an axis corresponding to the direction of gravity.

The set of antenna elements on the at least one auxiliary panel may beused in the antenna system to provide coverage to one or more sectors inthe area between the first radius and the second radius, represented bythe shading in FIG. 6. Each auxiliary panel 320, 322 may be tiltedmechanically or electronically to point towards the area between thefirst radius and the second radius. In addition, the set of antennaelements on the at least one auxiliary panel may be configured to form abeam having a smaller elevational coverage that the set on the centralpanel. For example, the elevational coverage may be approximately 32degrees from where the first sector ends, as depicted by arrows 330,332, 334, 336 and angles θ2 in the example of FIG. 3A. In other words,the sector corresponding to 0 to 50 degrees may be covered by thecentral panel, while the sector corresponding to 45 degrees to 77degrees may be covered by the antenna elements of each auxiliary panel.In this regard, there may be some overlap in the sectors between 45 and50 degrees. The total coverage provided by this example antenna systemmay therefore be 0 degrees to 77 degrees relative to a center of thecentral panel or an axis corresponding to the direction of gravitytoward the horizon. Therefore, when the HAP 114 is flown at 20approximately kilometers, 77 degrees of elevational coverage may reachapproximately 86.6 kilometers. The reduction in elevational coverage mayprovide greater gain at greater elevations than if the elevationalcoverage of the one or more auxiliary panels were the same as that ofthe central panel. In some cases, there may be overlap between thecoverage of the central panel and the coverage of the at least oneauxiliary panel, which may decrease the total elevational coverage ofthe antenna system.

For a plurality of auxiliary panels, the set of antenna elements on eachauxiliary panel may be used in the antenna system to provide coverage toa sector covering a portion of the area between the first radius and thesecond radius. The portion of the area may include an arclength of thearea. The arclength of the area covered by each auxiliary panel may beequal in size. FIGS. 7 and 8 are representative examples coverage areaconfigurations for the antenna system 218. Referring to FIG. 7 which maycorrespond to the example of FIGS. 3A and 3B, when there are fourauxiliary panels arranged around a central panel, the antenna elements(represented by sector 7A) of the central panel may cover an area of thefirst radius. In addition, the sets of antenna elements on eachauxiliary panel may cover at least approximately 90 degrees arclength(represented by sector 7B-7D) of the area between the first radius andthe second radius. Referring to FIG. 8 which may correspond to theexample of FIG. 4 or 5, when there are twelve auxiliary panels arrangedaround a central panel, the antenna elements (represented by sector 8A)of the central panel may cover an area of the first radius. In addition,the sets of antenna elements on each auxiliary panel may cover at leastapproximately 30 degrees arclength (represented by sectors 8B-8M) of thearea between the first and the second radius. The coverage provided by agiven auxiliary panel may be adjacent to or slightly overlapping thecoverage provided by a neighboring auxiliary panel.

The coverage area of a given auxiliary panel may be adjustableindependent from the central panel and any other auxiliary panels. Thecoverage for individual sectors may therefore be adjusted independentfrom other sectors. For instance, as noted above, the tilt of the atleast one auxiliary panel relative to the central panel may be anelectronic tilt. For example, an angle of a tilt of the given auxiliarypanel may be adjusted mechanically by one or more processors of the HAP,such as the one or more processors 210 of HAP 114 using a switchingsystem, such as that which is depicted in FIG. 9. In this example,various switches may be used to switch between two adjustable tilts fora set of antenna arrays for an auxiliary panel including 4 antennaelements, ANT1-ANT4. The angle of the tilt may be adjustable between 15degrees and 35 degrees below the horizon, between 105 degrees and 125degrees relative to the central panel, or any other range. Additionallyor alternatively, the one or more processors 210 may adjust the coveragearea by forming a beam using the antenna elements on the given auxiliarypanel to point at an angle. The angle of the tilt of the beam may bebetween 15 degrees and 35 degrees below the horizon, between 105 degreesand 125 degrees relative to the central panel, or any other range. Theone or more processors 210 may determine at what angle to point thegiven auxiliary panel or the beam for a given sector based on populationdensity, history of demand, presence of other terminals (terrestrialtowers, other HAPs, etc.) providing coverage in or near the area, orother network factors.

In some implementations, the set of antenna elements on an auxiliarypanel may also be steered to narrow or widen the area of coverageprovided by that auxiliary panel. For instance, steering may be achievedby changing the digital beam forming coefficients. For example, when t12 auxiliary panels are combined in a digital beam forming way, th12 maybe the coefficient used in the digital domain. If 6 auxiliary panels areused instead of 12, the coefficients could simply be changed. This maywiden the beam azimuthally. Another way to widen the beam is to changethe number of antenna elements used in each panel. For example, if anauxiliary panel has 5 antenna elements, instead of using all 5 antennaelements, 4 or 3 could be used. To do so dynamically, a feed board withswitches may be used, in order to enable different feed types (e.g.different antenna elements) to be switched on and/or off. The width ofthe area of coverage may also be determined based on population density,history of demand, presence of other terminals (terrestrial towers,other HAPs, etc.) providing coverage in or near the area, or othernetwork factors.

Additionally or alternatively, the central panel of the antenna system218 may be steerable. For example, the central panel may be mounted on agimbal that is configured to adjust the orientation of the central panelrelative to the HAP and thereby to adjust the pointing direction of theset of antenna elements central panel. In this regard, the one or moreprocessors 210 may steer a pointing direction of a spot beam formed bythe first set of antenna elements. In another example, the one or moreprocessors 210 may electronically steer a pointing direction of the spotbeam formed by the antenna elements on the central panel.

In addition or alternatively, the pointing direction of the spot beammay be computed outside of the HAP. For instance, the pointing directionmay be computed by some remote computing device on the ground. In agimbal-based steering system, information such as a current location ofthe HAP, the population (e.g. potential client devices and/or users ofthe network) on the ground, current locations of other HAPs (e.g. otherHAPs in the network), the amount of power left in the HAP, as well astime of day (night time, day time etc), can be used to determine anoptimal pointing direction for a gimbal-based antenna element. Once theoptimal pointing direction is determined, a signal identifying thisoptimal pointing direction may sent to the HAP, and the one or moreprocessors 210 may control the gimbal to achieve the optical pointingdirection for the antenna element. Alternatively, if using digital beamforming (instead of gimbal-based) system, the optimal coefficientrequired to point the beam at the appropriate direction could bedetermined using the aforementioned information. Again, a signalidentifying this information may sent to the HAP, and the one or moreprocessors 210 may utilize the optimal coefficient to control theantenna element.

The one or more processors 210 may also narrow or widen the area ofcoverage provided by the central panel. The pointing direction and thewidth of the area of coverage provided by the central panel may bedetermined by the one or more processors 210 or some remote computingdevice on the ground based on population density, history of demand,presence of other terminals (terrestrial towers, other HAPs, etc.)providing coverage in or near the area, or other network factors.

In some antenna systems, the communication system may include aplurality of auxiliary panels without a central panel. For instance, aseparate steerable antenna may be mounted on the HAP in place of thecentral panel. The separate steerable antenna may be configured toprovide narrow, high capacity coverage to a smaller geographic areawithin the large geographic area. The smaller geographic area may beselected dynamically by the one or more processors 210 based onpopulation density, history of demand, presence of other terminals(terrestrial towers, other HAPs, etc.) providing coverage in or near thearea, or other network factors. Alternatively, a similarly configured,separate steerable antenna may be attached to the central panel toachieve the same or similar coverage.

The frequency utilized for the separate steerable antenna may from ahigher frequency band than is utilized for the central and/or auxiliarypanels. For example, the frequency range utilized for the central and/orauxiliary panels may include 700 MHz, and the frequency range utilizedfor the separate steerable antenna may include 2.6 GHz or 3.5 GHz.

The features described herein may provide for a communication systemthat, when mounted on a HAP, increases coverage and capacity for anetwork. The antenna system may reach areas tens of kilometers in radiuswith more consistent, low capacity coverage and may also be used fornarrower, high capacity coverage for particular areas with a need forgreater bandwidth. As described, the communication system may flexiblyadapt to different network needs for a geographic area and may conserveresources as a result.

Unless otherwise stated, the foregoing alternative examples are notmutually exclusive, but may be implemented in various combinations toachieve unique advantages. As these and other variations andcombinations of the features discussed above can be utilized withoutdeparting from the subject matter defined by the claims, the foregoingdescription of the embodiments should be taken by way of illustrationrather than by way of limitation of the subject matter defined by theclaims. In addition, the provision of the examples described herein, aswell as clauses phrased as “such as,” “including” and the like, shouldnot be interpreted as limiting the subject matter of the claims to thespecific examples; rather, the examples are intended to illustrate onlyone of many possible embodiments. Further, the same reference numbers indifferent drawings can identify the same or similar elements.

The invention claimed is:
 1. A system comprising an antenna system for ahigh-altitude platform (HAP), the antenna system including: a centralpanel including a first set of antenna elements; a plurality ofauxiliary panels arranged about an axis perpendicular to and centered onthe central panel and at an angular offset from the central panel, eachauxiliary panel of the plurality of auxiliary panels including a secondset of antenna elements; and wherein the first set of antenna elementsin the central panel is configured to provide network coverage within afirst area having a first radius and each of the second sets of antennaelements in the plurality of auxiliary panels is configured to providenetwork coverage within a second area beyond the first radius.
 2. Thesystem of claim 1, wherein the plurality of auxiliary panels includes atleast 4 auxiliary panels.
 3. The system of claim 1, wherein theplurality of auxiliary panels includes at least 12 auxiliary panels. 4.The system of claim 1, wherein the central panel is arranged such thatwhen in operation on the HAP, the central panel is oriented or faces ina downward direction relative to the HAP.
 5. The system of claim 4,wherein the plurality of auxiliary panels is arranged such that when inoperation on the HAP, the plurality of auxiliary panels is oriented atan angle offset from the downward direction relative to the HAPcorresponding to a downward tilt.
 6. The system of claim 5, wherein thedownward tilt is a fixed orientation.
 7. The system of claim 5, whereinthe downward tilt is an adjustable orientation.
 8. The system of claim1, wherein the plurality of auxiliary panels is arranged such that whenin operation on the HAP, the central panel is recessed relative to theauxiliary panels.
 9. The system of claim 1, wherein the central panelincludes a planar surface on which the first set of antenna elements arearranged.
 10. The system of claim 9, wherein the central panel is aring.
 11. The system of claim 10, wherein the first set of antennaelements are arranged at regular intervals around the central panel. 12.The system of claim 1, wherein a coverage area of each of the pluralityof auxiliary panels is adjustable independent from the central panel andother auxiliary panels in the plurality of auxiliary panels.
 13. Thesystem of claim 1, wherein each of the second sets of antenna elementsare arranged in a linear array on a respective one of the plurality ofauxiliary panels.
 14. The system of claim 1, wherein the second set ofantenna elements is a plurality of antenna elements arranged linearlyalong a given auxiliary panel of the plurality of auxiliary panels; andwherein each of the second sets of antenna elements has a clover-shapemounted parallel to the given auxiliary panel.
 15. The system of claim1, wherein each of the plurality of auxiliary panels has a sameconfiguration.
 16. The system of claim 1, further comprising one or moreprocessors configured to electronically steer a pointing direction of abeam formed by the first set of antenna elements.
 17. The system ofclaim 1, further comprising a gimbal configured to adjust an orientationof the central panel relative to the HAP and thereby steer a pointingdirection of a beam formed by the first set of antenna elements.
 18. Thesystem of claim 1, wherein the plurality of auxiliary panels is arrangedsuch that when in operation on the HAP, the central panel is arrangedbelow the auxiliary panels.
 19. The system of claim 1, furthercomprising the HAP.
 20. The system of claim 19, wherein the HAP includesa balloon.